multiple sources to a single balanced voltage output

Other Hardware General Electronics
1

Hi everyone,

My project is simple :

I am building an RC vehicle that works with 11.1 volts and needs 2aH to work properly.. It should be powered up form a single 2200mAh 11.1V 4S LiPo battery, but will last only aprox 10-20 minutes...

I would like to know how to get a solution to have multiple sources ( 4 identical batteries and one solar pannell ) to a single output to keep an equal output charge throughout all the batteries ( either discharging them all at once equally during a big amount of time, or one by one from 100% to 10% each.... )

If anyone could help me fast, it'll be very much appreciated !

Thanks everyone !

Tanguy

2

You can’t parallel up the batteries and the solar panel seems pointless
.
You could monitor the voltage of the battery in use and switch in the next battery when it starts to fall ( not too easy with a lipo driving a motor)
But the switching process may well introduce unacceptable voltage drops or make your system crash out .
The extra weight of the batteries maybe an issue too .

The best bet is to buy a bigger battery , lighter/cheaper ?

3

It is better to just buy a larger battery. They are readily available up to 10Ah or even more. BTW 11.1V is 3S not 4S so don't get the wrong thing.

But you can parallel Lipo batteries to give greater capacity if you need to (and I have done so many times). They will share the current being drawn and will all discharge equally. Since it's not a very common thing to do you will probably need to make up your own 4 into 1 parallel lead using your preferred connectors. It is probably best to separate them for charging but charging as a single 8Ah battery will also work. It's not that long ago that all high capacity Lipos were made by paralleling several batteries.

I'm not sure a solar panel really has any place in such a high power system.

Steve

4

single 2200mAh 11.1V 4S LiPo battery

I beg to differ. A 4S battery is 16.5V to 17V charged. (4*4.3V)

The full charge voltage of a single cell is 4.2 volts but my experience is 4.3V, which puts the
full charge voltage of a 4S at somewhere between 16.8 & 17.2V.

Your above statement would only be valid if it said '3S' instead of 4S.

Each Lipo battery needs to be individually balanced.

to a single output to keep an equal output charge throughout all the batteries ( either discharging them all at once equally during a big amount of time, or one by one from 100% to 10% each.... )

If you use 5 SPST relays, one for each battery, one in series with the charger, you can close one relay,
monitor the battery voltage or elapsed time and then disconnect the charger and measure the battery
voltage. If too low, you can reconnect the charger and repeat this process until the battery voltage
(with the charger disconnected) is 12.45Vdc (the fully charged voltage for

5

LiPo and similar chemistries require charge balancing controller when being charged (*), and I suspect most of the one's you'll find are designed only to charge a battery that's unloaded.

If you want more battery capacity, get a bigger capacity battery.

If you parallel this needs to be done at the cell level, not battery level, so charge-balancing can be done. And you should only use identical cells with identical histories - basically you'd buy a pre-built pack for this with LiPo.

NiMH is a less critical battery chemistry if you want flexible approach to handling multiple batteries. They self-balance on trickle charge and don't explode in flames if you get things wrong.

(*) otherwise the battery will rapidly deteriorate to a dangerous state over charging cycles. LiPo packs should never be charged unsupervised even so. Most charge-balancers assume a specific charging cycle, ending up with a long period of trickle-charging during which balancing takes place.

6

MarkT:
If you parallel this needs to be done at the cell level, not battery level, so charge-balancing can be done. And you should only use identical cells with identical histories - basically you'd buy a pre-built pack for this with LiPo.

Paralleling at pack level for discharge is fine but it is definitely worth separating the packs for charging. That way they can/will be balanced though this doesn't really need to be done on every charge.

And while identical cells is certainly the ideal case simple experiments show that it is not essential. Indeed I've paralleled a brand new 3000mAh pack and an old 800mAh pack to see what happens over a few discharge/charge cycles. They share the load remarkably well, discharge evenly and stay in balance. The obvious fact that in parallel the packs must always maintain the same overall voltage is a lot of what does the magic.

Steve

7

Couldn’t you just find battery packs with onboard protection? Then you could just parallel them up and charge discharge as you wish then when one cell is fully discharged or charged it will shut itself down?

8

"Couldn't you just find battery packs with onboard protection?"

Easy to say. How easy is it to do ?
Can you post a link ?
What kind of "protection" exactly ?
Can it disconnect itself from the charger ?
Most if not all lipos have balancer connectors
designed to be plugged into the type specific
ballancer adaptor board that comes with the
charger. I had at least 4 different types with
my charger . However , there is only one
ballancer cable per charger. That means the
OP must have 3 or 4 chargers or charge each
battery one at a time. Even if he had relays
to control the charger/battery connection
he would still have to restart the charger
for each battery.

9

no need to be a turd, it was a question, not an answer. rasmell...

i was thinking of a cell, i think.

The cell has built in protection.

however, i see they have these modules which might help op.

10

Really ? (thank you for sharing)
How does that solve the OPs problem?

11

Solve? help.

The circuit board provides protection to his battery pack, so now he can provide a current limited supply to the battery packs and charge them in situ because the protection circuit will shut off each pack when voltage is above 4.5v....

He can also discharge them however he likes, he does not have to worry about discharging them equally because the protection on each pack will kick in once the voltage drops below 3v...

12

It should be powered up form a single 2200mAh 11.1V 4S LiPo battery, but will last only aprox 10-20 minutes...

I would like to know how to get a solution to have multiple sources ( 4 identical batteries and one solar pannell ) to a single output to keep an equal output charge throughout all the batteries ( either discharging them all at once equally during a big amount of time, or one by one from 100% to 10% each.... )

First off, the above is not valid because it states 4S and, as anyone knows, a lipo cell
is 4.2 to 4.3V per cell so 4 cells is 4 4.2 = 16.8‬V , whereas a "2200mAh 11.1V" Lipo battery is a 3S
(34.2= 12.6‬V) (my experience is 12.45V for 3S)

Based on this:

I am building an RC vehicle that works with 11.1 volts and needs 2aH to work properly.

is appears the "4S" above is a typo or just a mistake.

That being said, the &ad_id=337677495518&product_id=1107660USs&gclid=EAIaIQobChMIxZOh7IzD5wIVC5yzCh0LygXmEAQYDiABEgIZWPD_BwE&cur_warehouse=CN]charging board

is advertised at being intended for 18650 form factor lipo cells but a lipo cell is a lipo cell so these flat single cells would work the same.

The only problem as I see it is there is no datasheet and no mention of balancing. All it says it
'overcharge protection'. There is no mention of 'BMS' as there is with other similar products.

If you read the OP's statement above he says:

I would like to know how to get a solution to have multiple sources ( 4 identical batteries and one solar pannell ) to a single output to keep an equal output charge throughout all the batteries ( either discharging them all at once equally during a big amount of time, or one by one from 100% to 10% each.... )

which, implies either
A: He thinks a 12.6V lipo pack has 4 cells and he wants to charge and discharge them simultaneously
or
B: He's mistaken about how many cells there are in a 12.6V lipo battery and wants FOUR 2200mAh
batteries (for a total of 8800mAh) and wants to charge and discharge all of them .

( either discharging them all at once equally during a big amount of time, or one by one from 100% to 10% each.... )

Clearly the OP is not aware that if he told us the current requirement we could simply calculate how
long it would last. He says 10 to 20 minutes which could only mean 10 minutes if he has a lead foot
or 20 minutes if he is just putting around.
Case A: lead foot 2200mAh = 2.2A per hour
10 minutes = 60min/10min = 1/6th of an hour, which means he is drawing 6 times 2.2A (13.2A) for 10min.
Proof: 2.2A/13.2A = 0.166 hour
0.166 * 60 min = 10 min

Case B: Just putting around
20 min/10 min = 2 times as long , ergo drawing HALF as much current , ergo 13.2A/2 = 6.6A

I don't know about you , but

but will last only aprox 10-20 minutes...

seems to
imply that is not long enough and the whole object of his post is to extend the time, which means
one 3S lipos is not going to cut it and he wants FOUR 3S lipos , so he should change the title of
his post to :
"How to get 8800mA lipo pack and charge all at the same time.

Seems to me four of the Seiko 'protection circuits' (not billed as BMS circuits)

If you look at the datasheet for the chip used on that board there is no mention of 'balancing'.

None of the following terms imply BALANCING.
'overcharge protection'
'overdischarge protection'
'overcurrent protection'

(they simply imply not charging the cells past 4.2V each)
or discharging them beyond some level.
Anyone who is in RC knows that Lipo packs sold at hobby stores are clearly labeled with respect to
the discharge 'C' rating (25C/45C etc) meaning 25 times the battery mAh rating.
As seen here:
Turnigy 2200mAh 3S 25C Lipo Pack

whereas the single flat pack lipo and 18650 lipos either don't give the rating (like the flat pack)
or they use a different rating (max current)
18650 20A battery

You do the math: (20A/2.5Ah = 8C)

13

Thanks to all for your time and for replying !

Yes indeed, they are 3S 11.1 2200mah not 4S...

however, I have foud a quite interesting alternative to using this power source :

one 11.1 3S 2200mAh is powering up the main circuit (Esc -> receiver -> motor) and the rest of the batteries are controlled via a relay from the receiver and are connected to a charger that charge the main circuit battery... so I can manually switch on the charger when needed. However I could connect the relay to an arduino that automatically sitches on all independent batteries to the charger by monitoring the battery’s voltage...

And last thing, I do also believe that the solar pannel is unnecessary, but was the initial idea for the project.

Again, thanks to all !!

Tanguy